From: Sasha Levin <levinsasha928@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Pekka Enberg <penberg@kernel.org>, Avi Kivity <avi@redhat.com>,
Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>,
kvm@vger.kernel.org, asias.hejun@gmail.com, gorcunov@gmail.com,
prasadjoshi124@gmail.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
takuya.yoshikawa@gmail.com
Subject: Re: [PATCH v2 6/8] kvm tools: Add rwlock wrapper
Date: Mon, 30 May 2011 15:22:59 +0300 [thread overview]
Message-ID: <1306758180.14564.98.camel@lappy> (raw)
In-Reply-To: <20110530122027.GJ22324@elte.hu>
On Mon, 2011-05-30 at 14:20 +0200, Ingo Molnar wrote:
> * Sasha Levin <levinsasha928@gmail.com> wrote:
>
> > On Mon, 2011-05-30 at 14:55 +0300, Pekka Enberg wrote:
> > > On Mon, May 30, 2011 at 2:49 PM, Ingo Molnar <mingo@elte.hu> wrote:
> > > > [*] Would be nice if tools/kvm/ had a debug option to simulate 'lots
> > > > of RAM' as well somehow - perhaps by not pre-initializing it and
> > > > somehow catching all-zeroes pages and keeping them all zeroes and
> > > > shared? It would obviously OOM after some time but would allow me
> > > > to at least boot a fair deal of userspace. The motivation is that
> > > > i have recently received a 1 TB RAM bugreport. 1 TB of RAM mapped
> > > > with 2MB mappings should still be able to boot to shell on a 32
> > > > GB RAM testbox of mine, and survive there for some time. We could
> > > > even do some kernel modifications to make this kind of simulation
> > > > easier.
> > >
> > > Doesn't our mmap() overcommit work for you? IIRC, Sasha booted guests
> > > with huge amounts of overcommitted RAM.
> >
> > It should. I can (easily) boot 64GB guest on my 4GB laptop. We fail at
> > >64GB due to an issue with our mappings (I haven't investigated it yet)
> > - not due to running out of memory.
>
> Oh, that's neat. Btw., i think there should be an option to actually
> *force* blatant overcommit: if i typo the option i'd like the tool to
> tell me that i'm probably stupid and refuse to run with that (and
> suggest the force-overcommit option), instead of trying to swap itelf
> to death!
How much is a 'blatant' overcommit? KVM easily handles x32 of host RAM.
> How does this work in practice - i thought we memset() all of RAM
> during guest kernel bootup. That might have changed with the memblock
> allocator ... So the guest kernel does not touch all of that 64 GB of
> RAM, so your box wont OOM straight away?
We simply mmap() with MAP_NORESERVE.
--
Sasha.
next prev parent reply other threads:[~2011-05-30 12:23 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-30 8:30 [PATCH v2 1/8] kvm tools: Use correct value for user signal base Sasha Levin
2011-05-30 8:30 ` [PATCH v2 2/8] kvm tools: Remove wrong global definition of kvm Sasha Levin
2011-05-30 8:38 ` Ingo Molnar
2011-05-30 8:59 ` Sasha Levin
2011-05-30 8:30 ` [PATCH v2 3/8] kvm tools: Allow pausing guests Sasha Levin
2011-05-30 8:39 ` Ingo Molnar
2011-05-30 8:30 ` [PATCH v2 4/8] kvm tools: Pause/resume guest using SIGUSR2 Sasha Levin
2011-05-30 8:41 ` Ingo Molnar
2011-05-30 8:30 ` [PATCH v2 5/8] kvm tools: Add a brlock Sasha Levin
2011-05-30 8:30 ` [PATCH v2 6/8] kvm tools: Add rwlock wrapper Sasha Levin
2011-05-30 8:43 ` Ingo Molnar
2011-05-30 9:29 ` Pekka Enberg
2011-05-30 9:34 ` Sasha Levin
2011-05-30 9:40 ` Pekka Enberg
2011-05-30 9:46 ` Sasha Levin
2011-05-30 9:48 ` Pekka Enberg
2011-05-30 9:54 ` Ingo Molnar
2011-05-30 11:11 ` Takuya Yoshikawa
2011-05-30 11:12 ` Sasha Levin
2011-05-30 11:26 ` Takuya Yoshikawa
2011-05-30 11:39 ` Avi Kivity
2011-05-30 11:49 ` Ingo Molnar
2011-05-30 11:55 ` Pekka Enberg
2011-05-30 11:58 ` Sasha Levin
2011-05-30 12:20 ` Ingo Molnar
2011-05-30 12:22 ` Sasha Levin [this message]
2011-05-30 12:25 ` Avi Kivity
2011-05-30 12:23 ` Avi Kivity
2011-05-30 12:30 ` Pekka Enberg
2011-05-30 12:32 ` Avi Kivity
2011-05-30 14:10 ` Ingo Molnar
2011-05-30 14:30 ` Avi Kivity
2011-05-30 14:43 ` Ingo Molnar
2011-05-30 14:50 ` Avi Kivity
2011-05-30 19:32 ` Ingo Molnar
2011-05-30 12:04 ` Avi Kivity
2011-05-30 12:36 ` Ingo Molnar
2011-05-30 12:44 ` Avi Kivity
2011-05-30 12:46 ` Pekka Enberg
2011-05-30 12:48 ` Avi Kivity
2011-05-30 13:05 ` Sasha Levin
2011-06-03 7:27 ` Sasha Levin
2011-06-03 7:34 ` Ingo Molnar
2011-06-03 7:54 ` Sasha Levin
2011-06-03 19:31 ` Paul E. McKenney
2011-06-03 19:56 ` Sasha Levin
2011-06-03 20:22 ` Paul E. McKenney
2011-06-03 21:03 ` Sasha Levin
2011-06-03 21:20 ` Paul E. McKenney
2011-06-03 22:54 ` Sasha Levin
2011-06-03 23:05 ` Paul E. McKenney
2011-06-04 6:26 ` Sasha Levin
2011-06-04 16:30 ` Paul E. McKenney
2011-06-14 22:26 ` Sasha Levin
2011-06-14 23:42 ` Paul E. McKenney
2011-06-15 1:25 ` Sasha Levin
2011-06-15 4:22 ` Paul E. McKenney
2011-06-05 12:12 ` Avi Kivity
2011-05-30 14:16 ` Takuya Yoshikawa
2011-05-30 9:56 ` Ingo Molnar
2011-05-30 10:05 ` Sasha Levin
2011-05-30 10:13 ` Ingo Molnar
2011-05-30 10:22 ` Sasha Levin
2011-05-30 10:30 ` Ingo Molnar
2011-05-30 10:41 ` Sasha Levin
2011-05-30 8:30 ` [PATCH v2 7/8] kvm tools: Add debug mode to brlock Sasha Levin
2011-05-30 8:30 ` [PATCH v2 8/8] kvm tools: Use brlock in MMIO and IOPORT Sasha Levin
2011-05-30 8:47 ` Ingo Molnar
2011-05-30 8:56 ` Sasha Levin
2011-05-30 8:35 ` [PATCH v2 1/8] kvm tools: Use correct value for user signal base Ingo Molnar
2011-05-30 8:40 ` Sasha Levin
2011-05-30 8:49 ` Ingo Molnar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1306758180.14564.98.camel@lappy \
--to=levinsasha928@gmail.com \
--cc=asias.hejun@gmail.com \
--cc=avi@redhat.com \
--cc=gorcunov@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=paulmck@linux.vnet.ibm.com \
--cc=penberg@kernel.org \
--cc=prasadjoshi124@gmail.com \
--cc=takuya.yoshikawa@gmail.com \
--cc=yoshikawa.takuya@oss.ntt.co.jp \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox